1. Field of the Invention
This invention relates to apparatus that employs self-scanning light sensing arrays for precisely positioning a movable stage or determining the speed of motion. More specifically, it relates to the use of self-scanning arrays of photodiodes in determining the actual position of a movable stage or speed of a moving member.
2. Description of the Prior Art
It has been known in connection with the positioning of movable stages of microscopes and other instruments to employ mechanical means such as set screw means, micrometers and the like.
In other environments, it is also been known to employ various types of servo control systems for position sensing. See, generally U.S. Pat. Nos. 3,708,657; 3,934,187; 4,042,863; 4,087,729; 4,117,460; 4,146,924; 4,156,169; 4,187,456 and 4,223,257.
U.S. Pat. No. 4,042,863 discloses a light transmitter-receiver transducer having a diaphragm for incrementally controlling a motor drive system. The diaphragm has a programed pattern in order to control the amount of light that is permitted to pass therethrough.
U.S. Pat. No. 3,719,776 discloses means for photographing an image of a specimen which is projected onto a cathode ray tube through the scanning of the specimen and passage of an electron beam therethrough.
U.S. Pat. No. 3,932,733 discloses a system for focusing an optical system such as a microscope through the use of electronic means.
U.S. Pat. No. 3,864,564 discloses blocking of a light beam by means of a blood specimen disposed on a slide and cooperating with a logic circuit to produce a control signal.
In spite of the foregoing teachings, there remains a very real and substantial need for an effective, rapid and accurate means of positioning a movable stage with great accuracy such as is needed in medical uses for chromosome analysis, blood cells and tissue cells studies wherein microscope stage positioning must be accomplished reproducibly and automatically within a few microns.